I have a solar panel that is 39.5 inches wide. The distance between the side edge of the roof and the vent is only 40.5 inches. So it will be a tight fit. Anyone have any experience or thoughts on mounting in such a tight spot?

Make sure that you mount the panel in such a way as to prevent any shadow from the vent on the panel. This will severely reduce the power you get from the panel. Maybe you want to make sure that the mounting method you use raises the panel enough so that it won't be a problem.

Raising it a bit to be out of the shadow of the vent is a good idea. Only a inch or two will keeep it out of the vent shadows (at least when it is closed). I was really surprised when I got on the roof today, there sure is only a limited number of spaces to place a large solar panel. Ours is inly a 28 foot 5th wheel. 3 vents, skylight, A/C, antenna, and several plumbing vents sure does not leave much open space.

Cruz-in
I went thru the same thing, the only 2 options I could come up with were,
1. Use a smaller panel, which I did not want to do as they were higher in cost than the bigger panel size etc.

2. Raise the panel above the blocking obstruction,ie,(mine was 2 different sky lites), by raising it a couple of inches, this allowed me to move the panel back several extra inches which created more mounting space/room to get away from the end.

I don't really care if the skylite source was blocked, it didn't create any problems and allow me to mount 4 bigger panel instead of 6+ smaller panels etc. I am going to have to remove about 1/3 of the hand rail on the other end, which will not cause any problem either, just to get enough room for another 66"x38" panel on the front end.

I had orginally designed/planned to use 2" high mounts, then I changed and went with 5" high mounts that I machined slots into the bases to allow the panels to follow the roof contour/slope to help with rain/snow drainage off the panels etc, and provides more air circulation under the panel in the summer months when the panel will be flat mounted.

3 of my panel will be mounted/tilted using the 38" width and the other one will be mounted/titled using the 66" length and will have 2 stout tilting braces on each side, which should hold up to the sudden Micro wind burst we get ALL the time around here.

The other item I did was make a scaled drawing of my roof and ALL the stuff mounted up there, including the height of the AC, Tv/radio ant etc and anything else that may make a shadow on any of the panels, then made too scale sized panels, got a bigger piece of butcher paper and drew the roof out to scale.

I used a 1" = 1 foot scale, and figured out the winter time sun angle in my area of use, by using my 40,000cp flash lite I could then use the flashlite too create shadows during the critical solar hours of 10am to 2pm, I could move the panels to various areas and see if there was going to be any problems with space available and shadows etc.

Have you considered mounting the solar panel a inch outboard of the roofline? I know it is a little un-conventional, but really it will not hang off by nearly as much as the awning, and I don't hear people complaining their awning got ripped up while driving down the freeway.

By putting the bolts in the front and back of the panel, you can still tilt it too. What I used to mount all my panels is 6" long 1/4" thick X 2" angle aluminum from Home Depot. Mounting it about 1" above the roof improves ventilation, a cooler panel will make more power.

I drilled 3 holes 3/16" in the one side, and 1 hole 5/16" for a bolt into the panel. I used nutserts to mount the panel to the bracket, and 1/4-20 stainless steel tamper resistant bolts.

I know that this picture does not show the mounts very well, but it is free advice, and I don't feel like taking another picture.

You can see the mount on the passenger side, it is mounted left to right, with two store bought "Big Foot" mounts for that pair of panels. It came from RvSolarelectric.com along with the 2 - 45 wat panels, mounting kit, tube of sealant, 30' of #10-2 direct burial wire, solar controller for $750 in 1994 - a good deal back then. Now days the solar panel will be 195 watts for $275 at SunElec.com and other parts cost less than $500 for sure! The prices sure have come down. The pair of 120 watt panels (also in the back of that picture, they are over the drivers and passenger seats) where $429 back in 1999, when dollar was worth about 50% more than today.

The price of silicon crystal, that makes up about 50% of the solar panel's cost went from $300 a pound a year ago to around $75 a pound today. So the solar panel costs have come down too!